I agree, the seeds should have enough nutrients to get young plants off to a good start. If you have too much nitrogen in the mix at the wrong time, your seeds may fail to germinate or dampen off.
I would not start fertilizing until the true leaves appear. 1/4 strength is good if you are going to do it weekly. It is also suggested that you only fertilize 1/4 strength for three weeks and one week just water to flush out the salts.
I used to use miracle grow on everything and it grew lush and well. However, one year it rained for 42 days and nights and the plants were drowning so I did not fertilize that year and the next year it bloomed better. I paid for the that the year after though. Too much fertilizer will give you growth at the expense of bloom and fruit. The wrong combination in the fertilizer can adversely affect flowering and fruiting. So, I suggest that you switch to a slow release fertilyzer once they get planted out and while it is o.k. to continue to use a higher nitrogen for leafy plants like Asian greens and lettuce, fruiting and rooting crops like beets, radishes, tomatoes, peppers should have a fertilizer with slow N and lower nitrogen. Nitrogen for fruiting and rooting crops should be timed to the growth phases of the plant. Cabbabages, taro, potato,and beets like more alkaline conditions and lower N. Too much nitrogen for beets and other roots crops will end up with lots of tops and not a lot of bulb. Conditions that are too alkaline make nitrogen and micronutrients less available for acid loving plants like tomatoes, peppers, gardenia, and roses.
Miracle grow for acid loving plants, citrus food, and high nitrogen fertilizers are more acidic, especially if they contain micronutrients and sulfur
Bone meal, phosphorus, compost, and lime are alkaline
Pure peat moss is acidic, but most commercial peat moss has been limed to a pH of 6.0.